! gfortran -c module2.f90
! gfortran -c module1.f90
! gfortran -c hello.f90
!gfortran -o hello hello.o module1.o module2.o
program hello
  use module1, only: sub1
  use module2, only: sub3
  implicit none

  print *, 'This is main program'
  call sub1()
  call sub3()

end program hello